|Year : 1968 | Volume
| Issue : 3 | Page : 121-124
Effect of artificially raised intraocular pressure on visual fields by perilimbal suction cup method
P Awasthi, SP Mathur, MC Luthra
Department of Ophthalmology, Sarojini Naidu Medical College, Agra, India
|Date of Web Publication||24-Dec-2007|
Department of Ophthalmology, Sarojini Naidu Medical College, Agra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Awasthi P, Mathur S P, Luthra M C. Effect of artificially raised intraocular pressure on visual fields by perilimbal suction cup method. Indian J Ophthalmol 1968;16:121-4
|How to cite this URL:|
Awasthi P, Mathur S P, Luthra M C. Effect of artificially raised intraocular pressure on visual fields by perilimbal suction cup method. Indian J Ophthalmol [serial online] 1968 [cited 2020 Aug 6];16:121-4. Available from: http://www.ijo.in/text.asp?1968/16/3/121/37533
LAUBER  suggested that field changes in glaucoma are due to an altered relationship between high intraocular pressure and normal retinal vascular pressure. However, it is not true for low tension glaucoma, as McGUIRE  has pointed out that the most reasonable explanation for the progressive field changes in chronic simple glaucoma is arteriosclerotic changes in the nutrient vessels of the optic nerve. DRANCE  studied the susceptibility of an eye to raised intraocular pressure and investigated the effect of artificially raised intraocular pressure on visual fields. The present study is an attempt to correlate artificially raised intraocular pressure with the visual fields, for which the suction cup technique has been employed.
| Material and method|| |
The intraocular pressure (I.O.P.) was raised by a perilimbal suction cup with an inner diameter of 13.5 mm, outer diameter of 18.75 mm and a contact surface 3 mm wide. The patient was asked to lie down on his back. The eye under investigation was anoesthetised by 1% Anethaine drops. The suction cup was applied on the cornea with its flanks placed perilimbally. A negative pressure of 50 mm of Hg. was created by a suction machine and was maintained for 15 minutes. If the patient complained of severe pain, the suction was stopped earlier. The fields were recorded on a one meter Bjerrum screen. The tension and fields were recorded before and just after the appliation of the cup and every 5 minutes afterwards till the field and tension returned to original level.
83 human eyes including 36 normal eyes as control and forty seven with suspected or definite glaucomatous changes were studied. All the eyes had broad angles and those with medium or narrow angles were dropped from the study.
In normal subjects (36 eyes) the average rise of tension was 14.5 mm Hg. Schiotz. The effects on increasing the I.O.P. are shown in [Table - 1]. In the last two patients in the table who developed enlargement of the blind spot and sickle shaped scotoma respectively, both were over 50 years of age. The tension and the fields returned to pre-experimental level in an average time of 23 minutes.[Table - 1]
The remaining 47 eyes were sub-divided into four sub-groups as follows:-[Table - 2]
II Glaucomatous group (47 eyes)
In subgroup A , ten eyes were investigated, having frank gloucoma in one eye, the other being normal. The normal eyes were investigated. In 8 eyes the duration of suction was 15 minutes and two eyes could not tolerate the suction for more than 12 and 13 minutes respectively. The average rise of tension was 16.3 mm. Schiotz, the original tension being 16-20 mm (18.1 average) and the tension after application of suction 2638 mm (average 34.4).
Two eyes showed no field changes while the rest developed the following field changes.
Generalised field constriction 2 cases
(temporal 4 to 8 degrees nasal 5 to 7 degrees).
Enlargement of blind spot 2 cases
Baring of the blind spot 3 cases
Sickle shaped scotoma 1 case
In an average of 25.5 minutes the tension and field returned to the original level. These eyes were followed for 6 months and 6 eyes developed baring of the blind spot (1/1000). Two eyes showed no field change.
In subgroup B, 23 eyes of suspected glaucoma, having positive family history, doubtful temporal pallor of disc, and the tension ranging between 20 and 24 mm (average 21.9 mm) on Schiotz were investigated.
9 eyes could tolerate suction for 15 minutes, while the remaining 14 eyes could not tolerate it for more than 12-13 minutes. The average duration of suction was 13.5 minutes and average rise of tension was 15.8 mm. of Hg. Three eyes showed no field changes. Other 20 eyes developed field changes as below.
Generalised field constriction 7 cases
(temporal 5 to 9 degrees nasal 5 to 8 degrees)
Enlargement of the blind spot 10 cases
Baring of the blind spot 3 cases
The field and tension returned to pre-experimental level in an average of 28.5 minutes. 18 eyes were followed for 6 months, 14 eyes developed central field changes, some had baring of the blind spot, others had nasal constriction and four eyes showed no field changes.
In subgroup 'C', 10 cases with established glaucoma in one eye, there was suspicion of glaucoma in the other eye, because there was occasional rise of tension (2-5 mm of Hg) with no field changes. The distance vision was normal. I.O.P. was between 20 mm to 25 mm of Hg Schiotz (average 22.2 mm). Only 3 eyes could stand suction for 15 minutes. The average rise of tension was 16.8 mm. Nine out of the 10 eyes developed field changes as below.
Generalised constriction of field 2 eyes
(temporal 6 to 9 degrees nasal 5 to 9 degrees)
Baring of the blind spot 2 eyes
Enlargement of blind spot 2 eyes
Sickle shaped scotoma 1 eye
Tubular fields . 2 eyes
The field and tension returned to normal in an average of 32 minutes. The eyes were observed for 6 months. 8 eyes developed field changes of various nature, while two eyes remained normal.
In group D four eyes of early glaucoma were studied. The intraocular tension varied from 25-30 mm Hg, with baring of blind spot, no vision defect and slight nasal constriction of the field. None of the eyes could stand suction for 15 minutes and the duration of suction varied from 10 to 12 minutes. The average rise of tension was 14.8 mm Hg. All the eyes developed field changes after suction as below.
Tubular fields 3 cases
Sickle shaped scotoma with nasal contriction of field 1 case
The time taken for tension and the field to return to original level was 35.0 minutes.
As the original level of tension was low in normal cases, the suction could be done for 15 minutes, whereas in pre-glaucomatous and glaucomatous patients, as the original tension was higher, the eyes could not stand suction for 15 minutes.
It was observed that in pre-glaucomaous and glaucomatous eyes the tension rose earlier than in normal eyes and took longer time to touch normal.
The above findings show that the rise of tension per minute in control eyes was 0.96 mm Hg and it gradually rose to 1.34 mm Hg in more established glaucomatous eyes and took a longer time to return to normal.
The control group of cases showed 0.63 mm Hg fall of tension per minute, while in early glaucomatous cases it reached as low as 0.42 mm Hg per minute.
| Comments|| |
It was observed that pre-glaucomatous and glaucomatous eyes could not tolerate suction for 15 minutes. The rise of tension after suction was greater in pre-glaucomatous and glaucomatous eyes than in the normal control eyes. The time taken for the tension to come to normal was much greater in preglaucomatous and glaucomatous eyes than in normal eyes. In group 'A' the eyes had no field defect. After suction there was a definite field defect. These eyes after 6 months developed early field changes. It is concluded that field changes are due to ischaemia and the field returns to normal after the tension has touched to pre-experimental level and normal circulation is restored, the normal eye taking less time than the suspected or definitely glaucomatous eye. It has also been observed that the eyes which developed baring of the blind spot and other gross field defects were potentially glaucomatous.
It is evident that the suction cup method is one of the methods to diagnose pre-glaucomatous condition much before the symptoms appear. Other glaucomatous tests may also be carried out before giving the final diagnosis.
| Summary|| |
36 normal and 47 glaucomatous or glaucoma suspect eyes were studied. There was greater rise of tension in glaucoma suspect or glaucomatous eyes after the suction than in normal eyes. The field changes were due entirely to ischaemia. Eyes which developed blind spot changes or other gross field defects were considered potentially glaucomatous.
| References|| |
DRANCE, S. M. Studies in the susceptibility of the eye to raised intraocular pressure. A.M.A. Arch. Ophth. Chicago), 68, 478 (1962).
LAUBER, H.: Treatment of atrophy of the optic nerve Arch. Ophthal. (Chicago) 10, 555 (1936).
MeGUIRE, W. P.: The effect of Dicumerol on visual fields in Glaucoma. Trans. Am. Sec. 46, 96 (1948).
[Table - 1], [Table - 2], [Table - 3]